By Josh Perry, Editor
Researchers from the Moscow Institute of Physics and Technology (MIPT) discovered that the physical effect superinjection, which amplifies the concentration of electrons and holes in semiconductor layers, is possible in semiconductor structures consisting of a single material, according to a report from the institute.
Researchers discovered superinjection is possible in semiconductor homostructures.
Superinjection is an effect that significantly improves the performance of lasers and LED by increasing the concentration of electrons and holes, which in turn leads to an increase in these charge carriers recombining. Previously, this physical effect was produced by sandwiching a semiconductor between semiconductor layers with wider bandgaps.
“However, two arbitrary semiconductors cannot make a viable heterostructure,” the report explained. “The semiconductors need to have the same period of the crystal lattice. Otherwise, the number of defects at the interface between the two materials will be too high, and no light will be generated. In a way, this would be similar to trying to screw a nut on a bolt whose thread pitch does not match that of the nut.”
It was believed that homostructures could not support superinjection, but MIPT researchers demonstrated the effect with silicon and germanium at cryogenic temperatures and in diamond or gallium nitride at room temperatures.
“Superinjection can produce electron concentrations in a diamond diode that are 10,000 times higher than those previously believed to be ultimately possible,” the researchers found. “As a result, diamond can serve as the basis for ultraviolet LEDs thousands of times brighter than what the most optimistic theoretical calculations predicted.”
Researchers believe that this discovery indicates the viability of superinjection in a variety of semiconductors and for use in numerous applications.
The research was recently published in Semiconductor Science and Technology. The abstract stated:
“Diamond and many newly emerged wide bandgap semiconductor materials show outstanding optical and magnetic properties. However, they cannot be as efficiently doped as silicon or gallium arsenide, which limits their practical applicability.
“Here, we theoretically predict a superinjection effect in diamond p-i-n diodes, which allows for the injection of orders of magnitude more electrons into the i-region of the diode than doping of the n-type injection layer allows. Moreover, we show that the efficiency of electron injection can be further improved using an i-p grating implemented in the i-region of the diode.
“The predicted superinjection effect enables us to overcome fundamental limitations related to the high activation energy of donors in diamond and provides the opportunity to design high-performance devices.”